Question

A 1000 kg plane moves in a straight flight at constant speed. The force of friction on the plane is 1800 N. What is the net force on the plane.

Answer 1

Since it is moving at a constant speed, the force acting on it is the gravitational force.

This is the normal force.

Now the gravitational force is perpendicular to the frictional force.

The Normal force = mg

g = 10

N = 10 × 1000 = 10000 N

Given that the forces are perpendicular, the resultant force will be the hypotenuse force of the two forces.

By pythagorean theorem we have :

H² = 1800² + 10000²

H² = 103240000

H = √103240000

= 10160.71 N

Answer 2

The force of the gravity is actually slow down in the plane.

The moving object keeps up the acceleration.

The plane is moving only at the constant velocity.

The moving object changes the direction of the travel.

Therefore, the net force on the plane is zero. This is because of the kinetic and static friction.